Fires, chemical spills, toxic fumes and odors are an ever present danger to occupants of buildings, factories, mines, or the like, especially when an escape route or exit from the location is not readily available. Various portable devices have been devised to assist an occupant of such an area to escape from or remain for a limited time in the toxic environment before exhausting a breathable air supply. Many of these prior devices are provided with some types of oxygen canister of generator which produces oxygen which is fed into a mask or mouthpiece for breathing by the user. Still other types of devices attempt to reduce the rate of depletion of the breathable air and oxygen within a confined space, such as a hood, by the use of an adsorbent which removes the carbon dioxide and water vapor from the exhaled breath, which if not removed would hasten the depletion or lessen the percentage of oxygen in the remaining air.
Examples of such prior air survival units or breathing apparatus are illustrated in U.S. Pat. Nos. 148,868; 1,298,404; 2,045,907, 3,277,890, 3,604,416; and 4,231,359.
Although many of these prior devices are satisfactory in certain aspects and serve the desired function most of them are relatively expensive and bulky making them difficult to be stored in a compact space or carried by an individual. Many of these prior survival units use a mask or mouthpiece which fits tightly against the person's face covering the nose, mouth and eyes. These devices may not form an airtight seal for all individuals, for example, those having a beard.
Other of these prior devices use a hood which covers the user's head but requires that the source of oxygen which is located externally of the hood enter the hood by a tube such as shown in U.S. Pat. No. 3,565,068. This tube prevents an efficient airtight seal to be formed around the user's neck. Also, most of these prior devices require an externally located oxygen generation unit, such as shown in U.S. Pat. No. 3,565,068, which is either a pressurized canister of oxygen or an oxygen candle for producing the oxygen. These external oxygen supply units although providing a source of oxygen for the user can be dangerous, especially in a fire since they could increase the rate of combustion should they be exposed to an open flame.
Most of these prior devices only remove the carbon dioxide from the exhaled breath and not the water vapor which contributes considerably to the depletion of the remaining oxygen within an enclosed space such as a hood or face mask. Still another problem with known devices is that the particular adsorbents used to adsorb or remove the carbon dioxide and water vapor from the exhaled breath may become contaiminated over a considerable inactive time period rendering the device ineffective at the time of emergency.
Therefore, there is a need for an improved air survival unit which is compact, relatively inexpensive and lightweight which enables the user to breathe in a toxic environment for a sufficient period of time to escape therefrom, and in which means can be provided to increase the time that the user may remain in the hazardous environment.